Demography and Populations

Age At First Breeding; Intervals Between Breeding

Two of 227 banded chicks returned in first two years after hatch, although it is unknown whether or not they bred (Senner et al. unpubl.). Other godwits usually breed first at 2 yr old, occasionally 1 yr old (e.g., Haverschmidt 1963 Haverschmidt, F. (1963). The Black-tailed Godwit. Leiden, Germany: E. J. Brill. Close , Cramp and Simmons 1983 Cramp, S., and K. E. L. Simmons (1983). The Birds of the Western Palearctic, Volume 3: Waders to Gulls. Oxford University Press, Oxford, UK. Close ); probably annually thereafter (e.g., Gratto-Trevor 2000 Gratto-Trevor, C. L. 2000. Marbled Godwit (Limosa fedoa). In The Birds of North America, No. 492 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Close ).

Clutch

Typically lays 4 eggs. See Breeding: eggs, above.

Annual And Lifetime Reproductive Success

Few data. At Churchill, reports of 83% hatching success (30/36 eggs hatched, from 10 nests) in early 1960s (Hagar 1966 Hagar, J. A. (1966). Nesting of the Hudsonian Godwit at Churchill, Manitoba. Living Bird 5:5-43. Close ) and 85% success (39/46 eggs, 12 nests) during 1964–1967 (Jehl 1971b Jehl, Jr., J. R. (1971b). Patterns of hatching success in subarctic birds. Ecology 52:169-173. Close ). At Susitna Flats, hatching success was 95% (52/55, 15 nests) (Senner et al. unpubl.).

No information on lifetime reproductive success or on variables that influence reproductive success.

Number Of Broods Normally Reared Per Season

Never >1 documented; see Breeding: phenology, above.

Proportion Of Total Females That Rear At Least One Brood To Nest-Leaving Or Independence

In Churchill, ONT, 18% (n = 33) of females had at least one chick fledge (Senner et al. unpubl.).

Unknown. Similar-sized Marbled Godwit can live to 29 yr and has annual survival rates estimated as 87% and 96% (Colwell et al., Colwell et al. 1995 Colwell, M. A., R. H. Gerstenberg, O. E. Williams and M. G. Dodd. (1995). Four Marbled Godwits exceed the North American longevity record for scolopacids. Journal of Field Ornithology 2:181-183. Close , Gratto-Trevor 2000 Gratto-Trevor, C. L. 2000. Marbled Godwit (Limosa fedoa). In The Birds of North America, No. 492 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Close ). Minimum adult survival rates (i.e., banding return rates) for 8 large shorebird species, including Black-tailed and Bar-tailed godwits, averaged 76% per year (Reed et al. 1998d Reed, J. M., C. S. Elphick and L. W. Oring. (1998d). Life-history and viability analysis of the endangered Hawaiian Stilt. Biological Conservation 84:35-45. Close ).

Diseases

No information.

Body Parasites

Little information. No nematodes (Habronematoidea, Acuarioidea) in 3 birds sampled (Wong and Anderson Wong and Anderson 1990b Wong, P. L. and R. C. Anderson. (1990b). Ancyracanthopsis winegardi n. sp. (Nematoda: Acuarioidea) from Pluvialis squatarola (Aves: Charadriidae) and Acyracanthus heardi n. sp. from Rallus longirostris (Aves: Rallidae), and a review of the genus. Canadian Journal of Zoology 68:1297-1306. Close , Wong and Anderson 1991a Wong, P. L. and R. C. Anderson. (1991a). Distribution of gizzard nematodes (Habronematoidea, Acuarioidea) of New World shorebirds (Charadriiformes), with special reference to localities of transmission. Canadian Journal of Zoology 69:2579-2588. Close ). Two species of lice, Lunaceps paschalis and Rotundiceps cordatus, reported in a major review of Mallophaga (Malcolmson 1960 Malcolmson, R. O. (1960). Mallophaga from birds of North America. Wilson Bulletin 72: 182–197. Close ). Feather mites (Alloptes sp.) also found on birds at Churchill (McClure 1943a McClure, H. E. (1943a). Aspection in the biotic communities of the Churchill area, Manitoba. Ecological Monographs 13:1-35. Close ).

Little information. Incubating adults taken by foxes from 3 of 36 nests at Churchill (Jehl 1971b Jehl, Jr., J. R. (1971b). Patterns of hatching success in subarctic birds. Ecology 52:169-173. Close , J. R. Jehl, Jr. pers. comm., JK). Adults taken, at least occasionally, by Gyrfalcon (Kuyt 1980 Kuyt, E. (1980). Distribution and breeding biology of raptors in the Thelon River area, Northwest Territories, 1957-1969. Canadian Field-Naturalist 94:121-130. Close ). In both Churchill and Sustina Flats, Northern Harriers (Circus cyaneus) have been observed taking incubating adults. One bird found with mussel attached to its leg and, consequently, unable to fly until the mussel was removed (Andrews 1954, cited in Thompson and Ely 1989 Thompson, M. C., and C. Ely (1989). Birds in Kansas, Volume I. University of Kansas Museum of Natural History Public Education Series 11. Close ).

Initial Dispersal From Natal Site

Two of 227 chicks were resighted at their natal site within 2 yr after hatch (Senner et al. unpubl.). In other godwits, banded chicks occasionally resighted near their banding site (Colwell and Oring 1988b Colwell, M. A. and L. W. Oring. (1988b). Habitat use by breeding and migrating shorebirds in south-central Saskatchewan. Wilson Bulletin 100:554-566. Close , Gratto-Trevor 2000 Gratto-Trevor, C. L. 2000. Marbled Godwit (Limosa fedoa). In The Birds of North America, No. 492 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Close ), with males nesting closer to their hatching site than females in Black-tailed Godwit (Groen 1993 Groen, N. M. (1993). Breeding site tenacity and natal philopatry in the Black-tailed Godwit Limosa l. limosa. Ardea 81:107-113. Close ).

Fidelity To Breeding Site And Winter Home Range

Few data. Territories often reoccupied from year to year, and several instances of banded birds returning to their previous breeding sites (including both members of a pair in 3 consecutive years), demonstrate that site fidelity occurs (Gill and Tibbitts 1999 Gill, Jr, R. E. and T. L. Tibbitts. (1999). Seasonal shorebird use of intertidal habitats in Cook Inlet, Alaska. In Final Rep: USDI, U.S. Geol. Surv., Biol. Resour. Div., and OCS Study. Close , L. Tibbitts unpubl., J. R. Jehl, Jr., pers. comm., JK). In Black-tailed Godwit return rates to breeding areas 78% for males, 69% for females (Jonas 1979 Jonas, R. (1979). Brutbiologische Untersuchungen an einer Population der Uferschnepfe (Limosa limosa). Vogelwelt 100:125-136. Close ).

Most of the world's population winters at 2 disjunct sites: with Alaskan breeders on the Pacific coast of South America and Manitoba breeders on the Atlantic coast, suggesting that fidelity to nonbreeding sites is high, but there is little information on movement among wintering sites or fidelity to home range sites. One Churchill bird equipped with a data logger for two years returned to the same non-breeding site (Bahía Blanca; Senner et al. unpubl.).

Dispersal From Breeding Site

No direct information. Genetic studies indicate little dispersal among main breeding populations (Haig et al. 1997 Haig, S. M., C. L. Gratto-Trevor, T. D. Mullins and M. A. Colwell. (1997). Population identification of western hemisphere shorebirds throughout the annual cycle. Molecular Ecology 6 (5):413-427. Close ).

Home Range

Little information. Based on observations of territorial males and adults with broods, maximum breeding density estimated as 1 pair/15–20 ha at Churchill (J. R. Jehl, Jr., pers. comm.). At Susitna Flats, AK, however, 2 nests were approximately 200–300 m from each other (CSE). Home range of birds breeding at Susitna Flats includes disjunct nesting and foraging sites, with birds traveling from spruce bogs to tidal mudflats to feed during the incubation period (mean distance moved 2.9 km [range 2.7–3.1, n = 5 pairs]); females continued to make these trips after eggs hatched (Gill and Tibbitts 1999 Gill, Jr, R. E. and T. L. Tibbitts. (1999). Seasonal shorebird use of intertidal habitats in Cook Inlet, Alaska. In Final Rep: USDI, U.S. Geol. Surv., Biol. Resour. Div., and OCS Study. Close ).

Numbers

From 1982 to 1986, an estimated 45,500 individuals were found during exhaustive aerial surveys of the South American coastline (Morrison and Ross 1989a Morrison, R. I. G., and R. K. Ross (1989a). Atlas of Neararctic shorebirds on the coast of South America. Volume 1. Canadian Wildlife Service Special Publication. Ottawa, Ontario, Canada. Close ). More recent aerial surveys in Bahía Lomas (on Tierra del Fuego), combined with ground counts of Isla Chiloé (2002-2005), have provided a mean estimate of 35,000 individuals (Espinosa et al. 2006). These counts did not include a number of sites on Isla Chiloé, nor did they include Bahía San Sebastían (on Tierra del Fuego) or Bahía Samborombon, all of which potentially harbor large wintering concentrations (Andres et al. 2009). Taking all of this into consideration, a more accurate estimate is likely 50,000-70,000 individuals (Morrison et al. 2006).

Counts from elsewhere may provide important information on size of different breeding populations. During fall migration, >10,000 estimated at James Bay; 8,800 on Pen I., Hudson Bay; 3,400 at Luck Lake, SK; 2,900 at Quill Lakes, SK; and 2,000 at Porter Lake, SK (Morrison and Harrington 1979 Morrison, R. I. G. and B. A. Harrington. (1979). Critical shorebird resources in James Bay and eastern North America. Paper read at Trans. 44th N. Am. Wildl. and Nat. Resour. Conf., at Washington, D.C. Close , Morrison et al. 1995b Morrison, R. I. G., R. W. Butler, G. W. Beyersbergen, H. L. Dickson and A. Bourget. (1995b). Potential Western Hemisphere Shorebird Reserve Network sites for shorebirds in Canada. In Tech. Rep. Ser. no. 227. Ottawa: Can. Wildl. Serv. Close , Alexander and Gratto-Trevor 1997 Alexander, S. A., and C. Gratto-Trevor (1997). Shorebird migration and staging at a large prairie lake and wetland complex: The Quill Lakes, Saskatchewan. Canadian Wildlife Service Occasional Papers no. 97. Environment Canada, Ottawa, Ontario, Canada. Close , G. Beyersbergen unpubl. data). Up to several hundred Hudsonian Godwits also found along the coast of Hudson Bay between Churchill and the Manitoba-Ontario border, at Oak Hammock Marsh, MB, and at other lakes in Saskatchewan (Morrison et al. 1995b Morrison, R. I. G., R. W. Butler, G. W. Beyersbergen, H. L. Dickson and A. Bourget. (1995b). Potential Western Hemisphere Shorebird Reserve Network sites for shorebirds in Canada. In Tech. Rep. Ser. no. 227. Ottawa: Can. Wildl. Serv. Close , W. Renaud and G. Beyersbergen unpubl. data). In Alaska, as many as 5,000 individuals may stage at Aropuk Lake in the w. Yukon Delta (McCaffery et al. 2005); hundreds occur during late summer at Carter Spit on the southeast shore of Kuskokwim Bay (Seppi 1995 Seppi, B. E. (1995). Hudsonian Godwit migration at Carter Spit, Alaska. Western Birds 26:167. Close ) and in Cook Inlet (Gill and Tibbitts 1999 Gill, Jr, R. E. and T. L. Tibbitts. (1999). Seasonal shorebird use of intertidal habitats in Cook Inlet, Alaska. In Final Rep: USDI, U.S. Geol. Surv., Biol. Resour. Div., and OCS Study. Close ); hundreds, possibly low thousands, also use Cook Inlet during spring (Gill and Tibbitts 1999 Gill, Jr, R. E. and T. L. Tibbitts. (1999). Seasonal shorebird use of intertidal habitats in Cook Inlet, Alaska. In Final Rep: USDI, U.S. Geol. Surv., Biol. Resour. Div., and OCS Study. Close ).

Due to the high dispersion of pairs within breeding areas, surveys on breeding grounds give information on only a tiny fraction of the total population, and data are difficult to obtain. Nesting population of Churchill region has been estimated as 50–55 pairs within a study area of approximately 7,000 ha (W. Lin and J. R. Jehl, Jr., unpubl.). Densities on the outer Mackenzie Delta, NWT, estimated as average of 2.4 pairs/km² in sedge habitat (n = 30 plots, each 200 × 200 m) and 1.0 pairs/km² in wet sedge/willow or emergent habitat (23 plots); species was absent from upland tundra (15 plots) and tall wet-willow (10 plots) habitats. Population of the entire outer delta was estimated as 2,543 pairs within 3,988 km², based on extrapolation using Landsat estimates of each habitat's area (Gratto-Trevor Gratto-Trevor 1996 Gratto-Trevor, C. L. (1996). Use of lands at TM Imagery in determining important shorebird habitat in the outer Mackenzie Delta, N.W.T. Arctic 49:11-22. Close , Gratto-Trevor 1996 Gratto-Trevor, C. L. (1996). Use of lands at TM Imagery in determining important shorebird habitat in the outer Mackenzie Delta, N.W.T. Arctic 49:11-22. Close ).

Based on recent tracking data and band recoveries strongly linking Alaska breeding birds to those wintering on Isla Chiloé, the Alaskan population likely numbers >20,000 individuals (Andres et al. 2009; Senner and Johnson unpubl.). However the allocation of these individuals to different breeding populations within Alaska remains difficult. No data from other localities.

Trends

Few data and no current monitoring program adequate to document population-wide changes. Thought to have declined earlier in the century: e.g., fewer birds seen in the vicinity of Buenos Aires in the 1920s than were reported 50 yr earlier; this change attributed to hunting (Wetmore Wetmore 1926c Wetmore, A. (1926). Observations on the birds of Argentina, Paraguay, Uruguay, and Chile. United States National Museum Bulletin 133:1–448. Close , Wetmore 1927b Wetmore, A. (1927b). Our migrant shorebirds in southern South America. U.S. Department of Agriculture Bulletin 26. Close ). Reports of endangerment from North America in the early 1900s, and apparent changes in population size, have been difficult to assess because there have not been regular surveys at major staging or wintering sites. At Churchill, considered “very rare” in the 1930s (Taverner and Sutton 1934 Taverner, P. A. and G. M. Sutton. (1934). The birds of Churchill, Manitoba. Annals of the Carnegie Museum 23:1-83. Close ) and “common” in the 1960s (Hagar 1966 Hagar, J. A. (1966). Nesting of the Hudsonian Godwit at Churchill, Manitoba. Living Bird 5:5-43. Close , Jehl and Smith 1970 Jehl, J. R., Jr., and B. A. Smith (1970). Birds of the Churchill region, Manitoba. Special Publication no. 1. Manitoba Museum of Man and Nature, Winnipeg, Manitoba, Canada. Close ). Over-all change between 1930 and 1990 described as a “great increase” (W. Lin and J. R. Jehl, Jr., unpubl.).

Numbers in James and Hudson bays reported to have declined between the late 1970s and early 1990s (Morrison 1991 Morrison, R. I. G. (1991). Research requirements for shorebird conservation. Transactions of the North American Wildlife and Natural Resources Conference (1991):473-480. Close ). In the 25 yr in between Morrison and Ross's comprehensive aerial surveys and those undertaken by Andres et al. (2009), the number of total birds using Isla Chiloé and the adjacent mainland did not significantly decline, although the number of sites used by >1% of the flyway population did. This decline in site usage has, in part, prompted the creation of a long-term monitoring scheme in the region that should lead to a more accurate assessment of flyway population trends (Andres, Johnson, Senner unpubl.).

No information.